USTS and SPRAYS Vegetable Insects By J. M. Wright and J. W. Apple THE PURPOSE of this publication is to give commercial vegetable growers and home gardeners up-to-date information for use against insects that damage vegetable crops. It does not describe these insects, nor does it give their life histories to any extent. For information concerning identification and life histories, see Illinois Circular 671, entitled Common V egetable Insects. Write College of Agriculture, University of Illinois, Urbana, for free copy. GENERAL CONTROL MEASURES Insect control is too often thought of only as spraying or dusting; that is, as the use of insecticides. Several other practices, however, that require little or no expense help materially to reduce insect damage. Destroy insect breeding places. Weeds, crop wastes such as old cabbage stalks or melon vines, neglected fence rows, ditch banks, and neglected hotbeds and cold frames, all serve as breeding places for garden insects and protect them during the winter. Plow under, compost, or burn these crop remnants as soon as possible after harvest. Don't let weeds grow in or near the garden. Choose resistant varieties. Resistant varieties are not weakened by insect attack. When conditions are unfavorable, they (Circular 672) ILLINOIS COLLEGE OF AGRICUllURE ENSION SERVICE IN AGRICULTURE AND HOME ECONOMICS perafi on w ilh ILLINOIS STATE NATURAL HISTORY SURVEY
2 Circular No. 672 are therefore more likely to produce profitable crops than nonresistant varieties. Then too, insecticides are normally more effective on resistant varieties. Any varieties you choose should, of course, be adapted to your locality. Rotate crops. Group related crops - such as cabbage and cauliflower, cucumber and squash, potato and tomato - and plant them in a different location every year. Don't follow early radishes by cabbage, nor cabbage by radishes. These two crops are subject to attack by the same insects. Even home gardeners sometimes need to choose a new location when insects have become very troublesome. Use best cultural practices. Good cultural practices will reduce, both directly and indirectly, the number of insect pests. Plowing destroys insects that live in the soil, such as white grubs and wireworms. Keeping down the weeds and grass on which cutworm moths lay their eggs often reduces cutworm damage. Frequent cultivation controls, at least partially, some of the flea beetles. Also, plants kept in a thrifty, growing condition will tolerate a moderate infestation of insects without serious injury and will recover more rapidly than unthrifty plants. HOW INSECTS FEED Insects are grouped into two general classes according to their feeding habits: chewing insects and sucking insects. Typical chewing insects are cabbage worms, grasshoppers, and flea beetles. Since they eat out pieces of plant tissue, the injury chewing insects do can be easily seen. The plant tissue they eat eventually reaches their stomachs, so that an insecticide put on the stems and leaves will also find its way into their digestive systems. Such poisons are usually called stomach poisons. DDT, rotenone, and parathion are common stomach poisons. Typical sucking insects are aphids, leafhoppers, and squash bugs. Sucking insects insert their needlelike beaks into the plant tissue and suck out the plant juices in much the same way that
Dusts and Sprays for Vegetable Insects 3 a mosquito punctures the skin and draws out blood. The wounds they make are seldom easy to see. The crops they feed on, however, may become badly deformed, or wilt and die prematurely. Little or none of the surface tissue of the leaf or stem reaches the stomach of sucking insects. Consequently an insecticide must be used that will kill these insects when it comes in contact with their bodies or appendages. Such poisons are called contact poisons. Typical contact poisons are nicotine, rotenone, DDT, and parathion. Some of these also act as stomach poisons. INSECTICIDES FOR VEGETABLE INSECTS Because they are highly poisonous to both chewing and sucking insects, some of the newer insecticides have the reputation of being general-purpose insecticides. But even the best of theserotenone, DDT, and parathion - will not control all the insects commonly found on garden vegetables. Other insecticides, more limited in their effect, may be needed. General Purpose Insecticides Rotenone is derived fron1 the roots of certain tropical plants. It can be used on vegetables with little danger of injuring the plants or of leaving a residue poisonous to people. Though it is effective against many insect pests, rotenone usually fails to give the high degree of insect control that such synthetic insecticides as DDT afford. The Mexican bean beetle, however, is very susceptible to it. Rotenone is commonly sold as a O.5-to-1.0-percent dust. Emulsifiable rotenone concentrates are available for spraying. They should be used according to directions of the processor. DDT, a synthetic insecticide, acts as both a contact and a stomach poison. Its residues on vegetables remain poisonous to insects for an extended period. DDT decomposes slowly and therefore should not be used on the edible portions of vegetables near harvest time. DDT is made in two grades - technical and refined (also called aerosol). Technical DDT is injurious to vine crops (cu
4 Circular No. 672 cumbers, squash, etc.), especially when it is applied as a spray. Refined DDT is less injurious to such crops, yet equals technical DDT as an insect poison. DDT dusts are sold in 3-, 5-, and 10-percent concentrations. Wettable DDT powder and en1ulsifiable concentrates are available for spraying. Most wettable powders contain 50 percent DDT, but recent developments indicate the possibility of using one containing 90 percent or more. Emulsion concentrates contain 25 to 34 percent. Parathion, a new phosphate insecticide, has shown unusual promise for the control of many vegetable insects. Though it is being offered for sale at the present time, there is still much to learn about it - what its dosage should be, what insects are susceptible to it, and what its hazards to plants and animals are. We do know that PARATHION IS A DEADLY POISON. Because of the dangers to those handling or applying it, it is not recommended for general use. Even though highly effective for many purposes, it should not be used where a safer material will give satisfactory control. Its use is justified only when a situation definitely demands it and when the operator is in a position to use or enforce all the proper precautions. From the standpoint of the operator, wettable parathion powder in a water spray is the safest form of application. Wettable powders usually contain 15 percent of parathion and are used at the rate of 1 to 2 pounds to the acre. Parathion dusts containing 0.5 to 1 percent of the toxicant are available. But if you use them, you must take special precautions to protect yourself or your operator. If you are making extensive applications of parathion, you must wear a good dust mask and protective clothing. Take these clothes off as soon as you can and take a bath or a shower. Do not use parathion on the edible parts of vegetables within 30 days of harvest. Special Purpose Insecticides Nicotine sulfate (40-percent) is highly effective against aphids. In instances in which DDT does not control aphids, it can be combined with DDT sprays. Water sprays are commonly
Dusts and Sprays for Vegetable Insects 5 made with 1 to 2 pints of 40-percent nicotine sulfate in 100 gallons of water. Six pounds of soap must be added to such a spray to activate the nicotine. Nicotine dusts can be prepared at home by mixing nicotine sulfate with hydrated lime. To make a 3-percent nicotine dust, thoroughly mix 3 pints of nicotine sulfate with 50 pounds of hydrated lime in a tight container. Several small stones in the container will help to get even mixing. Do not breathe the nicotine fumes from the mixture. Nicotine dus}s and sprays are not effective against aphids unless the temperature is above 70 F. Pyrethrum is obtained from the flowers of certain plants. To insects it is primarily a contact poison. Residues remaining on plants are not considered hazardous to man. Pyrethrum extracts (pyrethrins) are prepared as dusts and liquid concentrates for spraying. DDT has largely replaced pyrethrum. Tetraethyl pyrophosphate (TEPP), a new phosphate insecticide, is a highly effective contact poison for aphids and red spiders. Like parathion, however, it must be handled with great care and not allowed to come in contact with the skin or eyes. Emulsifiable concentrates for spraying are the easiest form to get. The amount of tetraethyl pyrophosphate in these preparations has not been standardized, so when using them it will be necessary to follow the recolumendations of the manufacturer. Do not use more than is recommended for specific crops since some crops may be injured by overdosing. Mixed sprays must be used immediately for best results. Freshly mixed dusts containing as little as 0.75 to 1.0 percent tetraethyl pyrophosphate have been used successfully against aphids. Chlordane acts as a contact and a stomach polson. While chlordane is effective against a great many vegetable insects, it has not been used extensively in Illinois because of its relatively high cost. A few vegetable insects are more susceptible to chlordane than to other insecticides, and in such cases its use is justified. Grasshoppers, cabbage maggots, and white grubs are examples of insects more easily killed with chlordane than with the
6 Circular No. 672 older insecticides. Chlordane is available as a low-concentration dust and as a wettable powder and emulsifiable concentrate for spraying. Methoxy DDT is less injurious to vine crops than technical grade DDT and has shown some promise for control of the Mexican bean beetle. It is a chen1ical analog of regular DDT. Generally it is less poisonous than ordinary DDT to vegetable insects. Toxaphene is very effective against grasshoppers, but has no insecticidal advantage to warrant its general use in the vegetable garden. TOE (DDD) is a chemical relative of DDT, but it usually has no advantage over DDT in the control of vegetable insects. Benzene hexachloride is a highly effective contact and stomach poison but is not recommended for vegetable insects because -it has been shown to taint food crops. Lindane (gg-percent gamma isomer of benzene hxachloride) is a recently developed insecticide that may prove to have some value in vegetable insect control. Ryania is recommended for the control of the European corn borer, but not for other vegetable insects. It is derived from the stems of certain tropical plants. Ryania is sold most commonly as a 40-percent dust. Sabadilla is another insecticide derived from plants. It is effective against many sucking insects, particularly the squash bug. Because of its limited use, it is not readily available from local distributing agencies. DUST AND SPRAY FORMULAS The charts on the following pages give dust and spray formulas for use on large plantings. For home gardeners who need a smaller amount of spray, a table of measurements is given on page 7. This table will show how the measurements given in these formulas can be adjusted to lots of spray as small as a gallon.
Dusts and Sprays for Vegetable Insects 7 Suppose you want to make a gallon of nicotine sulfate spray for aphids. First look up aphids in the chart on page 8 and write down the nicotine sulfate spray formula (1 to 2 pints of 40-percent nicotine sulfate in 100 gallons of soapy water). Then turn to the table below. Find 1 pint in the 100-gallon column and its equivalent in the I-gallon column: 1 teaspoon. Therefore use 1 to 2 teaspoons of nicotine sulfate in 1 gallon of the spray. No adjustment of dust formulas is necessary for home gardens. Thorough coverage with dusts as with sprays is, however, desirable. MEASUREMENTS FOR SMALL QUANTITIES OF SPRAY (Based on formulas for 100 gallons) Fo r 100 gal. For 25 gal. For 5 gal. For 1 gal. 1 gal........ 1 qt. 13 lb. 3 lb. 1 qt............ 1 cup 3 lb. 2 tsp. 1 pt... 1f2 cup 1 % lb. 1 tsp. 1 lb.... % lb. 2% lb. 1 % tsp. 2 lb.......... 1f2 lb. 5 lb. 1 lb. 3 lb..... 3,4 lb. 7% lb. 4 % tsp. All measurements are standard and are level. lb. = tablespoon. tsp. = teaspoon.
DUST AND SPRAY FORMULAS FOR VEGETABLE INSECTS: Commercial Plantings (Unless otherwise stated, use 25 to 30 pounds of dust per acre or 100 gallons of spray) For directions for adapting amounts to home gardens, see page 7. (X) Insect DUST SPRAY Remarks General Feeders on Garden Crops Aphids 3-percent nicotine in 1 to 2 pints 40-percent nicotine sulfate Use nicotine dust or spray only when temperature is above 70 F. hydrated lime in 100 gal. soapy water -or - - or 0.75- to I-percent Tetraethyl pyrophosphate emulsion Use according to manufacturer's directions. TEPP (freshly made) concentrate - or - -or I-percent parathion 172 lb. 15-percent wettable parathion CAUTION: Do not use on edible portions of vegetables within 30 -or in 100 gal. water days of harvest. I-percent rotenone Recommended for pea aphids only. (40 to 50 lb. per acre) -or 5-percent DDT (35 CA UTION: Do not use on pea vines that will be fed to cattle. to 40 lb. per acre) c: Blister beetles 5-percent DDT 2 lb. 50-percent wettable DDT in 100 Apply whenever beetles are present. e gal. water -or- z 1 qt. 25-percent emulsifiable DDT in!:l 100 gal. water 0. "l Cutworms 5-percent DDT Use DDT and chlordane at concentra Apply on ground around newly tra nsplanted tomato and cab I\) - or - tions to provide 1 lb. of actual insecti bage plants. 5-percent chlordane cide to 100 gal. water.. Flea beetles 5-percent DDT Use sprays given above for blister Apply whenever beetles are present or injury is evident. beetles. Grasshoppers 5-percent chlordane 2 lb. 50-percent wettable chlordane in Treat grasshoppers in margins of field before they move to crops. -or 100 gal. water lo-percent toxaphene - or 4 lb. 50-percent wettable toxaphene in Low-gallonage sprays of chlordane and toxaphene are effective 100 gal. water against grasshoppers. -OT- Emulsifiable concentrates of either used according to directions on container White grubs (No recommendations) (N 0 recommendations) and Wireworms
Cabbage Insects Cabbage worms 3- to 5-percent DDT Use sprays given for blister beetles, p. 8. Begin treatment when worms first appear and repeat at 10-day - or - or - intervals until three applications have been made. (3 species) I-percent parathioll Use parathion spray given for aphids, Use rotenone after heads are well formed. p. 8. - or - - or 0.75-percent rotenolle Use emulsifiable rotenone concentrate according to directions on container. Cabbage maggot 5-percent chlordane Use wettable chlordane and emulsifiable concentrate at a dilution to provide 1 Apply pint of spray to each plant. Treat soil around main stem shortly after transplanting. Repeat treatment in 1 week if lb. of actual insecticide in 100 gal. water. maggot eggs are numerous. Aphids See treatment given 011 p. 8. NOTE: DDT applied for worm control may intensify aphid problem since DDT kills parasites and predators that attack aphids. But nicotine or tetraethyl pyrophosphate may be combined with regular DDT sprays to control aphids. o Potato Insects Q a. Leafhoppers 3- to 5-percent DDT Use DDT sprays given for blister bee Begin treatment as soon as adult leafhoppers appear on the lit tles, p. 8. foliage. Make 4 applications spacing them 10 to 14 days apart. "0 Parathion is poisonous to leafhoppers but does not afford the i; Colorado Use treatmellt givell for blister beetles, p. 8 One or two treatments should eliminate adults and larvae. long protection given by DDT. potato beetles < Flea beetles Use treatment given for blister beetles, p. 8. Treat young potatoes as soon as beetles or their damage appear. CQ Aphids See treatment given 011 p. 8. Nicotine or tetraethyl pyrophosphate may be combined with regular DDT sprays. Potato stalk borer (N0 recommelldations) (No recommendations) Sweet-Corn Insects Q 0 id :- European corn 5-percent DDT 3 lb.. 50-percent wettable DDT plus On market corn varieties, begin treatment with first egg hatching borer (40 lb. per acre) lb. wetting agent in 100 gal. water - or - (about June 15 for first-generation borers and Aug. 15 for secondborer generation). Repeat treatment every 5 days until four have been 3 qt. 25-percent emulsifiable DDT in made. Apply dust or spray on whorl (curl) of young plants and 100 gal. watel' on ear zone of older plants. (For more information see Illinois - or - Circular 646) 40-percent Ryania 6 lb. pure Ryania stems plus lb. wet (40 lb. per acre) ting agent in 100 gal. water Corn earworm 5-percent DDT Inject 72 medicine dropperful of me Dust silks every 3 days until 4 applications have been made, dicinal oil into silk channel after silks starting when silks first appear. are dry. Stalk borer (N0 recolllmelldatiolls) (N0 recommendations) Seed corn maggot (N0 recommelldations) (N0 recommendations) '0
Insect Hornworms Tomato fruitworms Aphids Striped and spotted cucumber beetles Squash vine borers Squash bugs Thrips Maggots Mexican bean beetles Dust and Spray Formulas - Continued DUST SPRAY Tomato Insects Remarks o 5-percent DDT 5-percent DDT See treatment given on p. 8. Use DDT sprays as given for blister beetles, p. 8. Use DDT sprays as given for blister beetles, p. 8. Make one application when feeding is noticed. Refined DDT is less injurious to tomatoes than technical DDT. Apply 3 times, spacing treatments 10 to 14 days apart and starting at first fruit set. Refined DDT is less injurious to tomatoes than technical DDT. Vine Crop Insects 3- to 5-percent refined grade DDT No DDT recommendation -or O.75-percent rotenone Use emulsifiable rotenone concentrate as stated on container 3- to 5-percent refined grade DDT Use DDT sprays as given for blister beetles, p. 8. 1O-percent sabadilla (N0 recommendations) -or 5-percent refined grade DDT Make first application when beetles first appear and repeat as often as necessary to keep plants protected. n. Apply only to base of main stem where eggs are laid. Treat 4 c: times, spacing treatments a week apart and starting with appear i ance of first eggs on main stem (late June to early July). z Apply insecticides only when adults or nymphs are noted on plants. DDT does not kill squash bugs quickly. 0 Onion Insects 5-percent DDT Use DDT sprays as given for corn -or borer, p. 9. 1-percent parathion - or - Use parathion spray as given for aphids, p.8. 5-percent chlordane Usesprays as given for cabbage maggot, p. 9. Begin treatment when the population of young thrips averages 5 per plant. Apply 4 times, a week apart. CAUTION: Do not use DDT or parathion on bunching onions. Rotenone dust or nicotine sulfate sprays are less dangerous to consumers. Apply to row when onions are about 1 inch high. Repeat in a week if maggot eggs are numerous. Apply spray with low pressure and put on enough to moisten the soil around the plants. Bean Insects O.75-percent.rotenone Use emulsifiable rotenone concentrate - or as stated on container. L-percent parathion Start treatment when yellow larvae begin to hatch from eggs. Repeat at weekly intervals until 3 applications have been made. Apply to undersurface of leaves. CAUTION: Do not use parathion after pods have formed.
Bean Insects- Concluded Bean leaf beetles Use treatments given for Mexican bean beetles. DDT is also effec tive against bean leaf beetles but not against Mexican bean beetles. Leafhopper 3- to 5-percent DDT Use sprays given for blister beetles, p. 8. Begin treatment when young leafhoppers are seen on underside of leaves. Apply 4 times at 10- to l4-day intervals. Parathion is poisonous to leafhoppers but does not give the long protection that DDT does. Bean weevil (No recommenda tion for field use) (No recommendation for field use) o Asparagus Insects ;: 3- to 5-percent DDT Use DDT sprays as given for blister Treat as needed to keep insects off spears or foliage. Use rotenone - or beetles, p. 8. during the cutting season. Common and spotted O.75-percent rotenone -orasparagus Use emulsifiable rotenone concentrate "g '" beetles as stated on the container. Q Insect Pests of Carrots, Sweet Potatoes, Beets, Spinach, Lettuce, Celery, and Dill? Use DDT sprays given for blister bee Treat crop as soon as young b ugs are noted on plants. Tarnished 3- to 5-percent DDT CQ tles, p. 8. plant bug 0- " 3- to 5-percent DDT Use DDT sprays given" for blister bee Treat crop as soon as worms begin doing damage. cr Garden tles, p. 8. ed webworm Carrot weevil (No recommendations) (N0 recommendations) Carrot leafhoppers 5-percent DDT Use DDT sprays given for corn borer, Start treatment when plants are 2 to 3 inches tall and repeat p. 9. each week for 4 weeks. Sweet potato 3- to 5-percent DDT Use DDT sprays given for blister bee Begin treatments as soon as beetles or larvae are noted on foliage. tles, p. 8. beetles (T ortoise beetles or "goldbugs") Sweet potato 3- to 5-percent DDT Use DDT sprays given for blister bee Treat crops as soon as bluish-colored beetles appear. I nsecticides tles, p. 8. are not effective against worms feeding on t he roots. leaf beetle Q :J a.. S- "
DUSTING AND SPRAYING EQUIPMENT Dusters are preferred by many growers for applying insecticides because they are faster than sprayers. Dusting, however, is usually less effective than spraying. Whether you use a hand or a power duster, apply the dust in. a way to cover the plants thoroughly. If you use power equipment, you will need two dust nozzles to the row for most vegetable crops. One nozzle to the row, however, may be enough on such crops as cabbage, onions, and carrots. Sprayers can be l1sed throughout the day while the use of dusters is limited to periods of low wind velocity. An insecticide applied in a spray sticks to the leaves better than one applied in a dust. Power sprayers which apply 50 to 200 gallons of spray to the acre give better insect control than the new low-pressure (weed) sprayers which apply only 5 to 15 gallons of spray to the acre. If a low-gallonage weed sprayer is employed, use the required amount of insecticide in whatever volume of water is used to the acre. For information concerning the control of any insects not included in this circular, write Entomologist, State Natural History Survey, Natural Resources Building, Urbana, Illinois. Urbana, Illinois November, 1950 Cooperative E xtension Work in Agriculture and Home Economics: University of Illinois, College of Agriculture, and t he United States Department of Agriculture cooperating. H. P. R USK, Director. Acts approved by Congress May 8 and J une 30, 1914. 10M-ll 50-44792